In the Midwest which also experiences relatively high humidity and a couple week span of 100+ degree weather. I'll also recommend the semi-naked solution. When I get home from work I'm shedding clothing as fast as I can so I can get down to my skivvies. I also live by myself, but the view isn't that bad :).
I have patio chairs that I use for seating in the summer. They're basically a fabric mesh stretched over a frame - much cooler and breathable compared to a dense couch cushion or a leather seated chair. I keep a fan centered on me at all times, just having the air blow over me seems to help.
I try to grocery shop at night or early morning if at all possible to beat the heat.
I try to eat mostly simple, cold foods during the summer. Salads, marinated vegetables, lightly steamed or stir fry dishes, cold soups and drinks, sometimes just fruit and cheese and nuts and veggies sliced up and eaten. I avoid using the oven at all costs, try to avoid using the cook range if at all possible. If I do have to cook or bake something, I'll try to do it at night.
I try to do most of my yardwork either late at night or early in the morning. The east facing side of the house receives some shade starting around 5:00 PM, while the west facing side of the house has some shade up until 11:00 AM, so I'll try to hide from the sun by alternating which sides I work on.
Overall, I kind of just try to keep it easy and not move so much during the summer. I know that sounds rather un-Mustachian, but since I can hustle and bustle at work or when I'm out in a public place (library, grocery store etc.) that is air conditioned, I can kind of slack off at home and keep things moving at a slower pace.
I have a finished basement, and I plan on moving down there for the month of July, possible August and a bit of September if it gets too hot on the main floor.